Railroad vehicles composed by coupling a plurality of vehicles adopt a vehicle unit system. In the vehicle unit system, a plurality of vehicles composing one railroad vehicle are mounted with: a pantograph, a power supply unit configured of main power devices, such as a main transformer and a main converter, and an auxiliary power supply device, and auxiliary devices including an air compressor etc.
For example, the main power devices are dispersedly mounted on four vehicles and four vehicles are taken as one vehicle unit. A plurality of the vehicle units are coupled to compose a railroad vehicle.
When vehicle units are coupled to compose a railroad vehicle, the railroad vehicle is provided with the same number of pantographs as that of vehicle units. Pantographs are prone to become a source of noise and it is desirable to reduce the number of pantographs.
Consequently, a high-voltage cable is installed on the roofs of a railroad vehicle and power supply units are connected with one another through the high-voltage cable to reduce the number of pantographs. A shinkansen train composed of 10 vehicles will be taken as an example. When the train is provided with four power supply units, the four power supply units are connected with one another through a high-voltage cable; therefore, a pantograph only has to be provided in two places.
A high-voltage cable between vehicles in a vehicle unit is connected through a high-voltage joint and a high-voltage cable between vehicle units is connected through a high-voltage joint or a high-voltage insulator.
If a problem such as a ground fault occurs in a high-voltage cable, it is required to separate (electrically cut off) the high-voltage cable involving a point of problem and sound high-voltage cables from each other to prevent the ripple effect of the problem.
To electrically separate a high-voltage cable connecting the power supply units of vehicle units, conventionally, an operator must conduct the work described below. The operator climbs onto the roof of a vehicle and separates a connecting wire connecting one high-voltage insulator and the other high-voltage insulator using a tool. This separating work is high-elevation work and sufficient care must be paid to safety.
Patent Literature 1 proposes a technology with respect to railroad vehicles in which a plurality of power supply units are connected with one another through a high-voltage cable. According to the technology, a plurality of power supply units can be separated from each other without climbing onto the roof of a vehicle.
A more specific description will be given. Patent Literature 1 describes that: a high-voltage circuit breaker is configured of a vacuum circuit breaker that interrupts power supply to a power supply unit and a mechanical circuit breaker that is connected to the vacuum circuit breaker and cuts off a plurality of power supply units from one another; the high-voltage circuit breaker is placed in an equipment box; and the equipment box is so constructed that the equipment box can be opened and closed and is installed underfloor of a vehicle. After the equipment box installed under the floor is opened, a connecting wire connecting one high-voltage insulator and the other high-voltage insulator of the mechanical circuit breaker with each other is separated by an operator using a tool. Thus the operator need not climb onto the roof of a vehicle and only has to conduct underfloor work to separate a high-voltage cable involving a point of problem and sound high-voltage cables from each other.